The Effect of Addition of Phosphorus to Li/MgO Catalyst on Oxidative Coupling of Methane

• Published in: Journal of The Japan Petroleum Institute Vol. 37; no. 2; pp. 202 - 208
• Main Authors: YAMAMURA, Masami, TSUZUKI, Naohide, OKADO, Hideo, WAKATSUKI, Toshiya, OTSUKA, Kiyoshi
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo The Japan Petroleum Institute 1994; Sekiyu Gakkai
• Subjects: Active site; Methane; Mixed oxide catalyst; Partial oxidation
• ISSN: 0582-4664
• DOI: 10.1627/jpi1958.37.202

The performance and physico-chemical properties of Li/Mg/xP catalyst (atomic ratio=1:1:x) for oxidative coupling of methane were investigated. A drastic change in the catalytic performance was observed by increasing the content of phosphorus. The maximum activity was obtained when phosphorus was added in a P/Li atomic ratio of 0.3; however, the maximum C2+selectivity was observed at the ratio of 0.1. The highest performance was obtained with Li/Mg/0.3P catalyst with the results: methane conversion of 39%, C2+selectivity of 50%, and C2+ yield of around 20%. The physico-chemical properties of Li/Mg/xP catalysts were investigated using the measurements of X-ray diffraction (XRD), BET specific surface area, and CO2 temperature programmed desorption (TPD); in addition, Fourier transformation infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were also used. The addition of phosphorus changed the form of lithium salt from Li2CO3 to Li3PO4, which brought about the change in the acid-base character of the catalysts. Low activity of Li/Mg/0.5P catalyst can be ascribed to the absence of Li2CO3. On the other hand, it is suggested that high activity of the Li/Mg/0.3P catalyst is due to the co-existence of Li2CO3 and Li3PO4 in the catalyst, which enables a good balance between acidity and basicity on the catalyst surface.